public GifFrame(Stream inputStream,
LogicalScreenDescriptor lsd,
ColourTable gct,
GraphicControlExtension gce,
GifFrame previousFrame,
GifFrame previousFrameBut1)
: this(inputStream, lsd, gct, gce, previousFrame, previousFrameBut1, false)
{
}
/// <summary>
/// Gets the base image for this frame. This will be overpainted with
/// the pixels for this frame, where they are not transparent.
/// </summary>
/// <param name="previousFrame">
/// The frame which preceded this frame in the GIF stream.
/// Null if this is the first frame in the stream.
/// </param>
/// <param name="previousFrameBut1">
/// The frame which preceded the previous frame in the GIF stream.
/// Null if this is the first or seond frame in the stream.
/// </param>
/// <param name="lsd">
/// The logical screen descriptor for this GIF stream.
/// </param>
/// <param name="gce">
/// The graphic control extension for this frame.
/// </param>
/// <param name="act">
/// The active colour table for this frame.
/// </param>
/// <returns></returns>
private static Bitmap GetBaseImage(GifFrame previousFrame,
GifFrame previousFrameBut1,
LogicalScreenDescriptor lsd,
GraphicControlExtension gce,
ColourTable act)
{
#region Get the disposal method of the previous frame read from the GIF stream
DisposalMethod previousDisposalMethod;
if (previousFrame == null)
{
previousDisposalMethod = DisposalMethod.NotSpecified;
}
else
{
previousDisposalMethod = previousFrame.GraphicControlExtension.DisposalMethod;
}
#endregion
Bitmap baseImage;
int width = lsd.LogicalScreenSize.Width;
int height = lsd.LogicalScreenSize.Height;
#region paint baseImage
switch (previousDisposalMethod)
{
case DisposalMethod.DoNotDispose:
// pre-populate image with previous frame
baseImage = new Bitmap(previousFrame.TheImage);
break;
case DisposalMethod.RestoreToBackgroundColour:
// pre-populate image with background colour
Color backgroundColour;
if (lsd.BackgroundColourIndex == gce.TransparentColourIndex)
{
backgroundColour = Color.Empty;
}
else
{
// TESTME: background colour index different to transparent colour
backgroundColour = act[lsd.BackgroundColourIndex];
}
baseImage = new Bitmap(width, height);
for (int y = 0; y < height; y++)
{
for (int x = 0; x < height; x++)
{
baseImage.SetPixel(x, y, backgroundColour);
}
}
break;
case DisposalMethod.RestoreToPrevious:
// pre-populate image with previous frame but 1
// TESTME: DisposalMethod.RestoreToPrevious
baseImage = new Bitmap(previousFrameBut1.TheImage);
break;
default: // DisposalMethod.NotSpecified
if (previousFrame == null)
{
// this is the first frame so start with an empty bitmap
baseImage = new Bitmap(width, height);
}
else
{
// pre-populate image with previous frame
// TESTME: DisposalMethod.NotSpecified on 2nd frame or later
baseImage = new Bitmap(previousFrame.TheImage);
}
break;
}
#endregion
return(baseImage);
}
/// <summary>
/// Sets the pixels of the decoded image.
/// </summary>
/// <param name="imageData">
/// Table based image data containing the indices within the active
/// colour table of the colours of the pixels in this frame.
/// </param>
/// <param name="lsd">
/// The logical screen descriptor for the GIF stream.
/// </param>
/// <param name="id">
/// The image descriptor for this frame.
/// </param>
/// <param name="activeColourTable">
/// The colour table to use with this frame - either the global colour
/// table or a local colour table.
/// </param>
/// <param name="gce">
/// The graphic control extension, if any, which precedes this image in
/// the input stream.
/// </param>
/// <param name="previousFrame">
/// The frame which precedes this one in the GIF stream, if present.
/// </param>
/// <param name="previousFrameBut1">
/// The frame which precedes the frame before this one in the GIF stream,
/// if present.
/// </param>
/// <param name="status">
/// GifComponentStatus containing any errors which occurred during the
/// creation of the bitmap.
/// </param>
private static Bitmap CreateBitmap(TableBasedImageData imageData,
LogicalScreenDescriptor lsd,
ImageDescriptor id,
ColourTable activeColourTable,
GraphicControlExtension gce,
GifFrame previousFrame,
GifFrame previousFrameBut1,
out GifComponentStatus status)
{
status = new GifComponentStatus(ErrorState.Ok, "");
Color[] pixelsForThisFrame = new Color[lsd.LogicalScreenSize.Width
* lsd.LogicalScreenSize.Height];
Bitmap baseImage = GetBaseImage(previousFrame,
previousFrameBut1,
lsd,
gce,
activeColourTable);
// copy each source line to the appropriate place in the destination
int pass = 1;
int interlaceRowIncrement = 8;
int interlaceRowNumber = 0; // the row of pixels we're currently
// setting in an interlaced image.
for (int i = 0; i < id.Size.Height; i++)
{
int pixelRowNumber = i;
if (id.IsInterlaced)
{
#region work out the pixel row we're setting for an interlaced image
if (interlaceRowNumber >= id.Size.Height)
{
pass++;
switch (pass)
{
case 2:
interlaceRowNumber = 4;
break;
case 3:
interlaceRowNumber = 2;
interlaceRowIncrement = 4;
break;
case 4:
interlaceRowNumber = 1;
interlaceRowIncrement = 2;
break;
}
}
#endregion
pixelRowNumber = interlaceRowNumber;
interlaceRowNumber += interlaceRowIncrement;
}
// Colour in the pixels for this row
pixelRowNumber += id.Position.Y;
if (pixelRowNumber < lsd.LogicalScreenSize.Height)
{
int k = pixelRowNumber * lsd.LogicalScreenSize.Width;
int dx = k + id.Position.X; // start of line in dest
int dlim = dx + id.Size.Width; // end of dest line
if ((k + lsd.LogicalScreenSize.Width) < dlim)
{
// TESTME: CreateBitmap - past dest edge
dlim = k + lsd.LogicalScreenSize.Width; // past dest edge
}
int sx = i * id.Size.Width; // start of line in source
while (dx < dlim)
{
// map color and insert in destination
int indexInColourTable = (int)imageData.Pixels[sx++];
// Set this pixel's colour if its index isn't the
// transparent colour index, or if this frame doesn't
// have a transparent colour.
Color c;
if (gce.HasTransparentColour && indexInColourTable == gce.TransparentColourIndex)
{
c = Color.Empty; // transparent pixel
}
else
{
if (indexInColourTable < activeColourTable.Length)
{
c = activeColourTable[indexInColourTable];
}
else
{
// TESTME: CreateBitmap - BadColourIndex
c = Color.Black;
string message
= "Colour index: "
+ indexInColourTable
+ ", colour table length: "
+ activeColourTable.Length
+ " (" + dx + "," + pixelRowNumber + ")";
status = new GifComponentStatus(ErrorState.BadColourIndex,
message);
}
}
pixelsForThisFrame[dx] = c;
dx++;
}
}
}
return(CreateBitmap(baseImage, pixelsForThisFrame));
}
public GifFrame(Stream inputStream,
LogicalScreenDescriptor lsd,
ColourTable gct,
GraphicControlExtension gce,
GifFrame previousFrame,
GifFrame previousFrameBut1,
bool xmlDebugging)
: base(xmlDebugging)
{
#region guard against null arguments
if (lsd == null)
{
throw new ArgumentNullException("lsd");
}
if (gce == null)
{
SetStatus(ErrorState.NoGraphicControlExtension, "");
// use a default GCE
gce = new GraphicControlExtension(GraphicControlExtension.ExpectedBlockSize,
DisposalMethod.NotSpecified,
false,
false,
100,
0);
}
#endregion
int transparentColourIndex = gce.TransparentColourIndex;
ImageDescriptor imageDescriptor = new ImageDescriptor(inputStream,
XmlDebugging);
WriteDebugXmlNode(imageDescriptor.DebugXmlReader);
#region determine the colour table to use for this frame
Color backgroundColour = Color.FromArgb(0); // TODO: is this the right background colour?
// TODO: use backgroundColourIndex from the logical screen descriptor?
ColourTable activeColourTable;
if (imageDescriptor.HasLocalColourTable)
{
_localColourTable
= new ColourTable(inputStream,
imageDescriptor.LocalColourTableSize,
XmlDebugging);
WriteDebugXmlNode(_localColourTable.DebugXmlReader);
activeColourTable = _localColourTable; // make local table active
}
else
{
if (gct == null)
{
// We have neither local nor global colour table, so we
// won't be able to decode this frame.
Bitmap emptyBitmap = new Bitmap(lsd.LogicalScreenSize.Width,
lsd.LogicalScreenSize.Height);
_image = emptyBitmap;
_delay = gce.DelayTime;
SetStatus(ErrorState.FrameHasNoColourTable, "");
return;
}
activeColourTable = gct; // make global table active
if (lsd.BackgroundColourIndex == transparentColourIndex)
{
backgroundColour = Color.FromArgb(0);
}
}
#endregion
// decode pixel data
int pixelCount = imageDescriptor.Size.Width * imageDescriptor.Size.Height;
TableBasedImageData indexedPixels
= new TableBasedImageData(inputStream, pixelCount, XmlDebugging);
WriteDebugXmlNode(indexedPixels.DebugXmlReader);
if (indexedPixels.Pixels.Count == 0)
{
// TESTME: constructor - indexedPixels.Pixels.Count == 0
Bitmap emptyBitmap = new Bitmap(lsd.LogicalScreenSize.Width,
lsd.LogicalScreenSize.Height);
_image = emptyBitmap;
_delay = gce.DelayTime;
SetStatus(ErrorState.FrameHasNoImageData, "");
WriteDebugXmlFinish();
return;
}
// Skip any remaining blocks up to the next block terminator (in
// case there is any surplus data before the next frame)
SkipBlocks(inputStream);
_indexedPixels = indexedPixels;
_extension = gce;
if (gce != null)
{
_delay = gce.DelayTime;
}
_imageDescriptor = imageDescriptor;
_backgroundColour = backgroundColour;
GifComponentStatus status;
_image = CreateBitmap(indexedPixels,
lsd,
imageDescriptor,
activeColourTable,
gce,
previousFrame,
previousFrameBut1,
out status);
WriteDebugXmlFinish();
}
